The integrated circuit (IC) manufacturing technology have been moving forward as the metal-oxide-semiconductor field-effect transistors (MOSFET's) become smaller and smaller to improve the performances such as increased switching speed, lowered power consumption and higher level of integration. In view of device isolation, shallow trench isolation (STI) technology has advantages over the conventional local oxidation of silicon (LOCOS) technology. For example, STI technology shrinks the surface area needed to isolate transistors while offering superior latch-up immunity, smaller channel-width encroachment and better planarity.
The STI structure is an integrated circuit (IC) feature that prevents current leakage between adjacent semiconductor components. Dual-depth STI structures have attracted attention for the applications in multi-functional IC devices. For example, on a typical panel driver IC device, deeper STI structures with better isolation are required for double-diffused drain (DDD) MOS elements and shallower STI structures with less dislocation are required for complementary metal-oxide-semiconductor (CMOS) elements
US Publication no. 20100252870 discloses a dual-depth STI structure having two different depths applicable to CMOS image sensor technologies, where the dual-depth STI structure refers to one STI structure in the pixel region and another STI structure in the periphery or logic region. The depth of each STI structure depends on the need and/or isolation tolerance of devices in each region.
However, the conventional dual-depth STI structure is manufactured by a two-step etching process, in which at least one trench defining mask is required for the deeper STI structure and another trench defining mask is required for the shallower STI structure.
In the present invention, a one-step etching process with etching selectivity between a sacrificial SiO2 layer and the Si substrate is employed to manufacture a semiconductor device with a dual-depth STI structure using only one trench defining mask for both the deeper STI structure and the shallower STI structure at the same time.